Stereoview cards contain a set of photographs taken by a camera with two lenses. The images are about 2.5 ” apart, which is approximately the distance between our eyes. When viewed in the prismatic lens of a stereoviewer, the brain perceives them as a single image in 3-D.
Stereoview cards are quite collectible today. They are relatively easy to find if you know where to look and show landmarks, genre scenes and important events. While not many of us alive today can remember when stereoviews were popular, many of us can remember the ViewMaster, which works on the same principle. (a nice bakelite viewmaster is a great thing to have too!)
Three images of the Brooklyn Bridge include one by the Keystone View Company from Meadville, Pa; one from William H. Rau in Philadelphia and one from Underwood & Underwood from New York. In 1920, the company sold most of its catalog of views to the Keystone View Company.
It’s difficult to determine the actual photographer of many of the images. Of particular interest is the work of William H. Rau, a noted landscape photographer who was at one point on assignment for the Pennsylvania Railroad. His work is in the collections of several American Museums including the Los Angeles County Museum of Art. Rau also photographed the 1904 Louisiana Purchase Exposition in Saint Louis, and the 1905 Lewis and Clark Exposition in Portland, Oregon. I am not sure how many of the images on cards with a Rau label were actually taken by him.